Heretofore, the emulsion has been applied by vertically slidable squeegees of a bucket type contacted at their front edges with the screen consisting of a screen material of silk, polyester, nylon or the like of a given mesh size and a frame surrounding the screen material. In this case, a manual moving operation requires a particularly high skill for applying a film of a uniform thickness. In order to overcome the difficulty of the prior art, there have been proposed various types of mechanically moving squeegees, as disclosed in U.S. Pat. No. 4,363,289 (corresponding to the Published European Patent Application No. 0026538). The U.S. patent relates to a method and an apparatus for applying an emulsion onto a screen printing, in which squeegees arranged at either side of the screen are advanced toward the screen face for contact therewith, and inclined to enable flow of the emulsion out of the squeegees at their front edges, the squeegees being vertically moved relative to the screen. With this prior art, the emulsion normally flows down from the squeegees so that the emulsion may be scraped by the front edge of the squeegee upon its upward movement to provide a uniform film thickness, whereas upon its downward movement (necessary for thick application) the emulsion may flow into the underside of the squeegee so that it is applied in different quantities, resulting in an irregular thickness. Upon application with the emulsion on both sides of the screen from its lower section, a certain distance between the screen face and the front edges of the squeegees is needed for giving a relatively thick emulsion film, because the squeegees may otherwise scrape off the applied emulsion. Thus, a screen with a larger emulsion thickness on its printing side cannot be produced. Further, the squeegees on both sides of the screen are symmetrically and synchronously moved by a single cylinder, so that one of the squeegees must be replaced by a rod or roller for application only on a single side of the screen, thus involving a troublesome replacement and resulting in a very difficult switchover for application of the emulsion from both sides to only one side of the screen or vice versa. Upon printing with the screen, application of the thicker emulsion on the printing side than on the ink-applying side is essential for obtaining a beautiful print, which is difficult with the prior art techniques described hereinabove. Further, since an arm for supporting and inclining the squeegees is supported on a slide which is slidably guided in a rail in order to move the squeegee forwards and backwards, and since a piston for inclining the squeegee is swingable during the noted forward and backward movement of the slide, correct control of the piston for inclining the squeegee is difficult after the end of the forward movement of the slide, and moreover, setting of the slide into the rail is troublesome, resulting in a construction necessistating the use of complicated and troublesome controlling means.
Thus, an object of the invention is to solve the above problems intrinsic in the prior art and to provide a method for applying a more uniform thickness of an emulsion over the entire surface of a screen, so that its ink-applying side is thin while its printing side is thick to enable production of a beautifiul print, this being accomplished by one of the squeegees being arranged on one side of the screen, for applying the emulsion, while the other is used for scraping and recovering the emulsion. Each of the squeegees is movable independently and only the emulsion applying squeegee may be inclined, with the emulsion being applied only during upward movement of the applying squeegee, while the uniform application of the emulsion through the screen mesh may be readily recovered.